Tool Steel Square Bar, Material Tool Steel, Material Grade O1, Thickness 0.25 in, Thickness Tolerance +0.015 in, Overall Length 18 in, Overall Width 1/4 in, Heat Treatable Heat Treatable, Heat Treatment Oil-Hardened, Mechanical Finish Mill, Yield Strength 58,000 psi, Tensile Strength 105,000 psi, Brinell Hardness 177 BHN, Rockwell Hardness 88 HRB, Standards ASTM A681, SAE J437, Includes Material Certificate Material Certificate with Lot Number, Length Tolerance +0.125 in/0 in, Shape Square